This can be done through the following steps:

For a query:
  1. Go to Control > Query
  2. Choose an Activities Query
  3. From the left, choose Activity Name
  4. Click Add
  5. Choose Equals
  6. From the dropdown menu, choose Unsubscribe All or Unsubscribe Email/eNewsletter
  7. Run the query
NOTE:  If you would like to query on unsubscribes from a specific Email/eNewsletter, you may use an additional criteria of Mailing Campaign Name Equals [Insert your Mailing Campaign Name]

For a report:
  1. Go to Control > Reports> People > Activity Summary
  2. Click Customize to set the date range and click Submit
  3. Click Drilldown on the Unsubscribe All or Unsubscribe Email/eNewsletter to view the results